Interaction of bacterial flagellum filaments with skeletal muscle myosin

Interaction of isolated bacterial flagellum filaments (BFF) and intact flagella from E. coli MS 1350 and B. brevis G.-B.p+ with rabbit skeletal myosin was studied. BFF were shown to coprecipitate with myosin (but not with isolated myosin rod) at low ionic strength, that is, under conditions of myosin aggregation. The data of electron microscopy indicate that filaments of intact bacterial flagella interact with isolated myosin heads (myosin subfragment 1, S1), and this interaction is fully prevented by addition of Mg2+ -ATP. Addition of BFF inhibited both K+ -EDTA- and Ca2+ -ATPase activity of skeletal muscle myosin, but had no effect on its Mg2+ -ATPase activity. Monomeric flagellin did not coprecipitate with myosin and had no effect on its ATPase activities. BFF were shown to compete with F-actin in myosin binding. It is concluded that BFF interact with myosin heads and affect their ATPase activity. Thus, BFF composed of a single protein flagellin are in many respects similar to actin filaments. Common origin of actin and flagellin may be a reason for this similarity.

[Longitudinal observations on the circulation of rotaviruses in Nizhny Novgorod using molecular-genetic methods]

1370 natural strains of human rotaviruses which circulated on the territory of Nizhny Novgorod during the period of 1984-1996 were differentiated with the use of electrophoretic typing of RNA. 58 electrophoretic types of RNA were detected; of these, 8 types dominated in the populations. The specific features of the circulation of strains with different electrophoretic types of RNA were characterized: co-circulation, time of domination, the change of the dominating genetic variant of the virus consecutively between seasons and during seasons. The change of domination during seasons, connected with the specific features of the circulation of rotaviruses having RNA of electrophoretic type 3, determined the winter-spring dynamics of the monthly detection rate of rotaviruses and was accompanied by an rise in the level of their detection. Such change was supposedly be caused by the biological properties of rotavirus with RNA of electrophoretic type 3, virulence constituting one of these properties. The study revealed that a change in the domination of the electrophoretic type of rotavirus, reflecting the change of the antigenic variant between seasons, occurred gradually during 5 seasons of the active circulation of strains.

[The detection of atypical human rotaviruses and their characteristics]

The electrophoretic typing of 1,370 rotavirus strains revealed the presence of group C rotaviruses in 1.3% of cases. In the Arkhangelsk region group C rotaviruses were detected in 34.4% of cases. The detected group C rotaviruses were shown to be no different in their morphology from typical ones; they were characterized by the variability of their genome and the absence of hybridization with RNA of group A rotaviruses. Group C rotaviruses were detected in children aged 3-6 years; in this age group they caused both sporadic morbidity and an outbreak of infection. The clinical manifestations of gastroenteritis caused by group C rotaviruses were no different from typical rotavirus gastroenteritis.

Comparison of Functional Load in Rat and Guinea Pig Hearts

Isolated rat hearts pump less cardiac output than guinea pig hearts at maximal volume load but develop higher left ventricular systolic pressure at increased resistance. These results allow us to understand the meaning of underlying peculiarities in the structure and function of cardiomyocytes of these two species.

[Functional significance of 2 pathways of energy transport in cardiomyocytes]

To study the relative roles of creatine kinase (CK) and adenylate systems in cardiac energy turnover, the effect of CK inhibitor, iodoacetamide- (IAA, 0.5 mM), and 2-deoxyglucose-(DOG, 2 mM) induced) 65% depletion of adenine nucleotides at slightly decreased CK flux was determined in isolated rat heart. Both substances did not substantially affect contractile parameters of the isovolumic heart. However, an augmentation of cardiac work induced by isoproterenol addition was feeble and transient in IAA-treated hearts while the response of DOG-treated hearts was well preserved. The cardiac failure after IAA treatment was associated with irreversible fall in myocardial ATP content as evidenced by 31P-NMR technique. Furthermore, these hearts were unable to perform cardiac pump function due to insufficient cardiac filling and distensibility. The DOG-treated hearts exhibited 50% reduction in the pump function and were able to increase their work in elevated resistance. The results suggest that CK pathway is extremely important for both full cardiac relaxation and maximal contractile function.

[The electrophoretic typing of rotaviruses in the clinico-epidemiological study of infection]

The electrophoretic study of the RNA of human rotavirus strains (1146 strains) circulating in 9 cities at the territory of the European part of the RSFSR was carried out. The electrophoretic (EP) types of rotavirus were established in each individual area. The study revealed that the most widespread rotaviruses responsible for the majority of gastroenteritis cases are those with the long EP type of RNA, characterized by the joint migration of segments 2, 3 and 7 (the 3rd EP type of RNA). Rotaviruses with the 3rd EP type of RNA much more often induce a severe course of rotavirus gastroenteritis in children aged 8 months to 3 years.

[An analysis of the gene coding for the basic neutralizing antigen VP7 of human rotavirus isolate 1407]

A procedure based on polymerase chain reaction was developed for the study of rotaviruses. A full-length cDNA copy of the gene coding for major neutralizing glycoprotein VP7 of a human rotavirus isolate 1407 with the "long" electrophoretype (classified as the first electrophoretype) was cloned and sequenced. The primary structure of glycoprotein VP7 of isolate 1407 in A and C antigenic regions was found to be similar to that of serotype 1 virus.

[The detection of rotavirus RNA in nasopharyngeal smears by molecular hybridization]

Rotavirus RNA was detected in nasopharyngeal washings, obtained from patients with rotavirus gastroenteritis (76.3% of cases) and gastroenteritis of unknown etiology (34.7% of cases), by the method of molecular hybridization with the use of RNA of monkey virus SA11, labeled with 32P in the process of T4-ligase reaction. In 100% of cases this detection correlated with the presence of lesions of the upper respiratory ways and was probably indicative of the rotavirus nature of the catarrhal syndrome in rotavirus gastroenteritis.

[Use of the polymerase chain reaction for analysis of rotaviruses. Nucleotide sequence of a gene, coding for the basic neutralizing antigen VR7 of a human rotavirus with a new G-serotype]

A procedure based on polymerase chain reaction use for the detection of rotavirus has been developed. Full length cDNA copy of the VP7 gene coding for the major neutralization glycoprotein of the human rotavirus RK9 with an unusual "wide" electrophoretype is cloned and sequenced. Glycoprotein VP7 of RK9 has a unique amino acid composition in A and C antigenic regions. It shows that strain RK9 represents a new (12) rotavirus serotype.

[Electrophoretic analysis of genome RNA of human rotaviruses]

The schemes for profiles of migration of RNA segments from human rotaviruses isolated in Gorky city in 1981-1987 are presented. The groups of the "long", "short" and "wide" electrophoretypes were identified. The dominant rotaviral phoretypes are determined. The possibilities of electrophoretyping and prospects of the future research are discussed.

Adaptation of cardiac contractile function to conditions of chronic energy deficiency

Left ventricular (LV) contractile function and pump function were depressed in isolated working hearts from rats treated with either guanidinopropionic acid (GPA), an inhibitor of creatine influx, or the anthracycline antibiotic, adriamycin, for 6 and 10 weeks, respectively. In both groups of treated animals myocardial phosphocreatine content was lower than in control hearts, while ATP content was unchanged. Hearts of treated animals exhibited only a minor depression of cardiac output with a submaximal pressure load or during volume overload. However, at maximal pressure load GPA- and adriamycin-treated hearts performed 43% and 37% less pressure-volume work than control hearts. These changes were due both to decreased LV pressure development and diminished cardiac output. LV diastolic stiffness was significantly higher at the submaximal pressure load and the LV filling pressure area, which reflected LV filling, was lower in hearts of both treated groups. The differences in both indices were exaggerated when the maximal pressure load was applied. Limited LV filling due to incomplete myocardial relaxation appeared to represent the underlying cause of cardiac failure when afterload was increased. These results may be explained if adaptation of cardiac contractile function in some chronic cardiac diseases arises from a limited energy supply to the myofibrils.

[Relation of cardiac diastolic elasticity to its adaptation to loading]

The pump function of the isolated rat or guinea pig hearts was assessed at various functional loads. The diastolic left ventricular (LV) stiffness was determined by a ratio of a rise in LV pressure for a diastole to LV filling volume for a diastole. This index was several times lower for guinea pig's hearts as compared to the rat hearts at equal heart rate. It was associated with a higher cardiac output of guinea pig hearts at low left atrium filling pressure. The rat hearts, however, having a higher diastolic stiffness adapted better to increased resistance or elevated heart rate, preserved the cardiac output and markedly increased cardiac work. The data obtained suggest that LV diastolic stiffness is an important factor determining cardiac adaptation to various functional loads; its influence seems to be actualized through changes in the LV filling.

The cardiac contractile failure induced by chronic creatine and phosphocreatine deficiency

Rats were fed a diet containing beta-guanidinopropionic acid (GP), an inhibitor of creatine transport. After 6 to 8 weeks of feeding the myocardial creatine (Cr) and phosphocreatine (PCr) stores were severely depleted while ATP content was normal. Hearts of GP-treated rats perfused according to Neely's working heart model revealed clear cardiac contractile failure: the maximal work capacity at a stepwise increase in resistance as well as the maximal oxygen consumption were 32 to 40% less in the GP group. The cardiac failure in GP-treated working hearts was associated with a rise in the left ventricular diastolic pressure, which could cause a diminished cardiac output probably due to impaired LV filling. The extent of the contractile failure was found to depend on functional load and on the degree of Cr (PCr) substitution. The energy fluxes through creatine kinase measured by the 31P-NMR saturation transfer technique were diminished by a factor of two after substitution of 90% of creatine, but still exceeded the rate of ATP turnover. The results are compatible with the concept of phosphocreatine pathway for intracellular energy transport and show that PCr is an important high energy phosphate compound for cardiac contractile function.

[Cardiac relaxation and distensibility in energy deficit]

Changes in the cardiac pump function, contractility, relaxation and distensibility in progressive metabolic blockade induced with dinitrophenol, were compared in the guinea pig isolated heart. A fall in relaxation and distensibility occurred first and was more obvious than a fall in contractility or the cardiac output. The same relationships were observed in isolated hearts of rats with myocardial phosphocreatine deficiency. The fall in relaxation and distensibility seem to be the necessary sign of acute or chronic myocardial energy deficiency.

[Contractile function of the isolated heart in chronic adriamycin-induced myocardial lesions]

Adriamycin, administered to rats for 4 weeks, caused insufficiency of isolated heart contractility with a twofold reduction of cardiac output in surviving animals. The same cumulative dose of adriamycin, administered to rats over 10 weeks, was not associated with any significant reduction of the heart's pumping function. However, heart rate increase by atrial electrostimulation that shortened the diastolic pause to a control level, also reduced the minute and stroke volumes by 38%, as compared to the controls. All animals showed increased diastolic stiffness of the left ventricle that must have interfered with its filling, particularly so in case of low inflow pressure, and disturbed atrial automaticity, as reflected in bradicardia in rats and supraventricular arrhythmia in guinea pigs.

[Compensatory factors in acute failure of the isolated heart]

The cardiac output of isolated guinea-pig hearts fell during progressive infusion of Ca2+-complexon, EGTA, or oxidative phosphorylation inhibitor dinitrophenol. Moderate doses of EGTA (0.3-0.6 mM) caused an apparent diminution of the left-ventricular +dP/dt and aortic pressure amplitude but did not influence cardiac output, which was maintained due to a prolongation of the contraction time. When the left-atrial cavity was greatly reduced by ligation, cardiac output fell by 40 per cent while left-ventricular systolic pressure and +dP/dt remained unchanged. In these conditions, EGTA in the same concentration reduced cardiac output by 30 per cent thus proving the important role of the left atrium in the compensation of hypocalcemic heart failure. On the contrary, the infusion of dinitrophenol shortened contraction time and increased myocardial rigidity. The latter change facilitated force development thus contributing to a lesser fall of +dP/dt and aortic pressure amplitude at equal diminution of cardiac output as compared to EGTA action. However, this compensation required a higher elevation of the filling pressure for inflow maintenance.

[Comparative analysis of the action of 2 calmodulin inhibitors on the contractile function of the isolated heart]

Ca2+-complexon EGTA and two calmodulin inhibitors: metaphenazine and trifluoperazine, induced similar effects on the cardiac contractile function: they diminished cardiac output, decelerated left ventricle pressure fall and increased both minimal--and end-diastolic pressure. Changes in the left ventricular pressure and its time course were more obvious during calmodulin inhibitor action as compared to EGTA at equal diminution of cardiac output. Trifluoperazine decreased left ventricular systolic pressure and resistance of coronary arteries to a greater extent than metaphenazine. The findings suggest participation of calmodulin in the regulation of myocardial relaxation mainly.

[Structural study of the basal bodies of the flagella of Bacillus brevis var. G.-B. P+]

The structural organisation of the flagellum basal body was studied in Bacillus brevis var. G.-B. P+ by electron microscopy. It was compared with that of Escherichia coli MS 1350. The basal body of a B. brevis flagellum contains, in addition to two pairs of rings on a rod, another ring-like structure (d = 13.6 nm, h = 4.3 nm) which we referred to as a "collar". The collar makes the basal body of B. brevis different from that of B. subtilis, another Gram-positive bacterium. The collar seems to fasten the flagellum of B. brevis to the cell wall. We have concluded that the basal body can differ not merely among bacterial systematic groups, but also among bacteria belonging to one and the same genus. The role of individual elements in the structure of the basal body of bacterial flagella is discussed.

[Interaction of bacterial flagella with myosin]

The interaction of isolated flagellar filaments of Bacillus brevis var. G.-B. P+ with skeletal muscle myosin has been investigated. Bacterial flagellar filaments co-precipitate with myosin at low ionic strength (at the conditions of myosin aggregation). Addition of bacterial flagellar filaments to myosin led to inhibition of its K+-EDTA- and Ca2+-ATPase activity, but had no influence on Mg2+-ATPase. Monomeric protein of bacterial flagella filaments (flagellin) did not co-precipitate with myosin and had no influence on its ATPase activity. The flagella filaments did not co-precipitate with myosin in the presence of F-actin if it was mixed with myosin before the filaments. If the flagella filaments were added to myosin solution before the addition of F-actin the amount of filaments and actin in myosin precipitate were comparable. In this case the presence of flagella filaments decreased activation of myosin Mg2+-ATPase by actin to 25-30%. Thus the bacterial flagellar filaments are able to interact with myosin and modify its ATPase activity. Probably, these properties of filaments are caused by resemblance of flagellin and actin. For instance, the unique origin of these proteins may be the reason of such resemblance.

[Effect of increased mechanical loading on the relation between the contraction of isolated cardiac muscle and the concentration of Ca++ in the perfusate]

The distension of isolated papillary muscles working isotonically or a transition to isometric working entailed an increased sensitivity of the contractile velocity to changes in perfusate Ca++ concentration. After sudden fall in Ca++ concentration, a more rapid decline of the contractile velocity in isometric mode was observed as compared to isotonic mode of working. The similar difference was found in experiments on isolated guinea pig heart working in isovolumic or auxotonic modes, though the rate of Ca++ loss by the heart was the same. The results suggest that an increased mechanical load may diminish the ability of myocardial cells to compensate for the changes in external Ca++.